Method to Study Solar Wind| NASA

Solar wind is a stream of energized charged particles, primarily electrons and protons, flowing outwards from the surface of the Sun, through the solar system at speeds as high as 900 km/s and at a temperature of 1 million degrees (Celsius). Aurora is one of the most beautiful naturally occurring events which attracts people across the globe & solar winds are responsible for them, same phenomenon happens on Jupiter. Solar winds are also destructible forces & it is said that they blew away Mars’s atmosphere millions & billions of years ago.

NASA & various other space agencies all over the globe are planning to send more & more spacecrafts, satellites to space but to prevent them from the side-effects of solar winds we need to understand how these occur.

So now i am going to discuss a method of studying the solar winds as proposed by Miss Samantha Wallace (PhD candidate at the University of New Mexico). I came to know about this method when i was scrolling across NASA's official website.

Here are the different steps involved in this method:

Starting  with a Magnetogram

The very first step in this process is to create a magnetic map of the Sun. Then start with the photosphere (solar surface), where the magnetic fields can be imaged with special cameras(We will only consider the photosphere which faces the planet Earth & towards NASA’s Advanced Composition Explorer or ACE spacecraft, which detects the solar wind.)

After all of this is done we will move towards the next step which is capturing a picture of Sun’s Earth-facing side but this process is difficult as sun keeps on moving. It is observed that Sun rotates by about 13 degrees every day, completing one full revolution — known as a Carrington rotation — about every 27 days.

To overcome this challenge snapshots of the Earth-facing side of the Sun as it rotates are taken day by day. Each snapshot reveals a slightly different portion of the Sun. A new part comes into view while an old part rotates past the horizon. Once the Sun completes a full Carrington rotation, they combine together the images into a single rectangular plot. The result gives us a 2-dimensional map that contains information about the entire surface of the Sun at the moment it was facing Earth.

Image down below shows how the magnetic map of solar surface will look like.

1. The top and bottom of the graph represent the north and south poles of the Sun respectively. 
2. Along the left and right, graph depicts the Sun’s Earth-facing surface as it rotated a full 360 degree. Different shades of gray show the strength and direction of the magnetic field. Darker colors represent magnetic fields that point in towards the Sun, lighter point away & medium is a neutral magnetic field.

This map doesn’t tell us where the solar wind truly originates. After it leaves the surface, the hot gas passes through tangled magnetic fields until it reaches the corona. There at the Sun’s outer atmosphere it can escape and become the solar wind. Now we move on to the next step.

Model the Corona

Till now scientists are not able to directly measure the magnetic fields in corona so scientists use models to predict how the magnetic field at the solar surface transforms as it expands outwards.

Now using a model coronal magnetic field is estimated, firstly the photospheric field is observed then moving outwards assuming that trends will work in same way by a distance about two and a half times the diameter of the Sun, coronal magnetic field is estimated.

Image down below represents what it looks like:

1. On the upper half, the uniform dark gray shows magnetic fields pointing in toward the Sun. 
2. On the bottom half, light gray shows magnetic fields pointing away. 
3. North and south meet in the middle at the yellow line. This line marks the heliospheric current sheet where the Sun’s magnetic field abruptly changes direction.

Sun’s magnetic field is complex and rippled, but by the time we reach the corona, magnetic field becomes smooth as it empties into the solar wind.

Connect It to the Spacecraft

Once the solar wind exits the corona, it travels more or less in a straight line. Now a new model is used that follows individual parcels of solar wind along those straight paths until they reach ACE.

Image down below shows how it actually looks like:

1. Red vertical lines  marks parts of the Sun directly in front of ACE as it collects measurements, they also note the date when ACE measured a specific parcel of the solar wind.
2. The yellow lines connect the solar wind ACE measures at that time to their origins on the surface.

After the data is collected by spacecraft it can be easily read & observed by the scientists on the ground station.

With the 2018 launch of NASA’s Parker Solar Probe, scientists have entered a new era in the study of the solar wind. As Parker passes closer to the Sun than any spacecraft before it, it is observing the solar wind in its freshest state yet. These observations will be key to prying open new questions about the solar wind and the complicated processes on the Sun that produce it.The German-American Helios mission, launched in 1974, flew as close as 27 million miles from the solar surface. 

Peace☮